1. Field of the Invention
The present invention relates to an exfoliative clay and a derivative thereof and, more particularly, to an exfoliative clay and a derivative thereof which are intercalated and exfoliated with a copolymer of polyoxyalkylene amine and polypropylene-grafting-maleic anhydride (PP-g-MA). The present invention also relates to a method for producing the exfoliative clay and the derivative thereof. In such a process, the intercalating copolymer can be recycled and delaminated silicate plates are obtained.
2. Description of the Related Technology
Currently, inorganic/organic-polymer composite nanomaterials are one of the most significant materials, and thus have been widely investigated and developed. Such composite nanomaterials are dual-phased wherein at least one phase is dispersed under a nanoscale regime. In order to obtain good dispersion, compatibility of the two phases, for example, clay and polymers, is always essentially important.
For the layered hydrophilic silicate clay, the interspaces or interlayer distances can be enlarged and become looser or more compatible after intercalated with an intercalating agent, and thus monomers or polymers are allowed to enter therethrough. The monomers or polymers can be further polymerized or copolymerized to obtain an exfoliative inorganic/organic-polymer composite material. The inorganic silicate clay is generally existed in the organic polymers at approximately 1–5 w %.
Conventional intercalating agents such as 12-aminolauric acid, hexadecylamine, fatty amine, bis(2-hydroxyethyl) methyl tallow alkyl amine and stearylamine, usually have low molecular weights, and consequently the enlarged interlayer distance of the clay is limited.
Referring to the research of T. J. Pinnavaia (Michigan State University), montmorillonite (MMT) is intercalated with an intercalating agent CH3(CH2)n—NH3+, and then exfoliated with diglycidyl ether of BPA (epoxy resin Shell Epon828) to form an epoxy/clay composite nanomaterial through self polymerization of the epoxy resin at 75° C. The structure of the intercalating agent may be monolayer, bilayer, or pseudo-trimolayer, and therefore the interlayer distance of the clay can be enlarged to 13.8–18.0 Å, which allow the epoxy resins to polymerize therein. The exfoliated nanomaterial is 34.1 Å in size and has an improved heat distortion temperature.
Japanese Patent No. 8-22946 discloses the first commercial inorganic/organic-polymer composite nanomaterial, which is developed by Toyota company. This composite material is produced by dispersing [H3N+(CH2)11COO−]/MMT in Nylon 6, wherein the aminocarboxylic acid is provided as an intercalating agent and the polymers are formed between layers of the clay through condensation of caprolactam monomers. However, the aminocarboxylic acid doesn't facilitate apolar polymers such as polyethylene and polypropylene, to uniformly disperse in the hydrophilic layered silicate. To solve this problem, Japanese Patent Publication No. 8-53572 provides organic onium ions as an intercalating agent, which can be uniformly dispersed in molten polyolefin resins. Unfortunately, though the organic onium ions can enlarge the interlayer distances, affinity between the intercalating agent and the polyolefin resin is not enough to exfoliate the layered silicate. Further, Japanese Patent Publication No. 10-182892 indicates that when blending with a molten mixture containing polyolefin resin and olefin oligomers having H-bond, the organized layered silicate might be indefinitely exfoliated due to the strong affinity therebetween. However, it's a dilemma whether to increase the oligomers for better dispersing or to decrease the oligomers for better mechanical characteristics.
Accordingly, there is a need to ameliorate the composite materials by means of providing appropriate intercalating agents, whereby the modified clay can exhibit good interfacial and compatible effect.